The present invention relates to a circuit for monitoring contact between the resistance track and the wiper of a potentiometer providing an adjustable DC voltage which is tapped from the wiper.
In safety-relevant desired-value or actual-value transmitters such as in a system for the electric control of the engine power (E-gas-system) in a motor vehicle, serious consequences can result from a lack of contact between the wiper and the resistance track of a potentiometer. In addition to other safety devices, for instance the provision of switches at predetermined potentiometer positions, a circuit for monitoring the internal resistance of a transmitter is known in which the transmitter is so connected to an oscillator that the internal resistance of the transmitter controls the oscillating ability of the oscillator and in which the output voltage of the oscillator is fed to a demodulator (German patent document 36 43 945 Al). In this known circuit arrangement, however, the coupling of the oscillator to the output of the transmitter is relatively expensive. Furthermore, the known circuit requires a separate oscillator which oscillates independently of other circuits, or does not oscillate.